Process for removing acid components from hydrocarbon solutions



Patented May 30, 1939 2,160,632

UNITED STATES PATENT OFFICE PROCESS FOR REMOVING ACID COMPO- NENTS FROMHYDROCARBON SOLUTIONS David Louis Yabroif, Berkeley, and Ellis R. White,Albany, CaliL, assignors to Shell Development Company, San Francisco,Oalifl, a corporation of Delaware Application May 7, 1937, Serial No.141,358

2 Claims. (Cl. 196-32) This invention relates to the removal of weaklybonates and bicarbonates, etc., although the hyacid-reacting organicsubstances from solutions droxides of the alkali metals are preferred.Espein hydrophobe organic liquids and in particular cially useful arethe sodium and potassium hydeals with the removal of mercaptans frompedroxides as being the strongest of the easily avail- 5 troleumdistillates. able bases. 5

It is frequently necessary to eliminate small It has already beenproposed to use saturated quantities of organic acidic components suchas substantially anhydrous solutions of caustic alkali mercaptans andphenols, etc., from their soluin ethylene glycol. We have found,however, that tions in organic liquids. By hydrophobe organic causticalkali are soluble in anhydrous ethylene l0 liquids, as herein referredto, are meant hydroglycol to a very limited extent only and thatconphobe normally liquid organic substances which siderably greaterquantities of caustic alkali can are neutral or slightly basic, such asthe liquid be dissolved in ethylene glycol which contains hydrocarbonsderived from petroleum, benzene, substantial amounts of water. Thesolubilities of toluene, xylene, substituted normally liquid hysodiumhydroxide in ethylene glycol of varying drocarbons which aresubstantially insoluble in contents of water were found to be asfollows: 15 water, for instance, chlorinated hydrocarbons, of Saturationvalues of NaOH in aqueous ethylene which chlorethane, ethylenedichloride, trichlorglycol solutions at C. ethylene, carbontetrachloride, chloropropane,

chlorbutylene, chlorbenzene, brombenzene, are Percentethfl NaOH no} 20examples; or nitro hydrocarbons, for example, on g ycol mality gonitroethane, nltrobenzene; or other nitrogen containing hydrocarbonssuch as amyl or higher 100 amines, aniline, quinoline, petroleum bases,etc. i3 2 3 In the U. S. Patent 2,059,075, by Yabroif and 25 Givens, itwas shown that the efiicacy of the re- 0 2s moval of acidic organicsubstances from their" solution in hydrocarbon type liquids by means ofThe eii'ect of the greater concentration of alkali 1 tm solutions whichare suhstahhydroxide which saturated ethylene glycol solutiallyimmiscible with said liquids, depends largely tions containingrelatively large amounts of water on the solvent power of the alkalinesolution for can hold is that the extraction efiiciencies of the 30 tOrganic acids and on t alkalinity of t saturated solutions increase withincreasing confo -men As a means e producing aqueous alkatents of water.In the attached drawing the line solutions of good solvent power forrganic amount Of mercaptans removed from a California acid the use ofquaternary ammonium bases wa gasoline by treating same saturatedsuggested. The addition of m polyhydmxy sodium hydroxide solutions inethylene glycol is 35 alcohols, not including ethylene glycol and glycShown- AS may be Seen the extraction efficiency erin, was disclosed inthe Yabroif applicati decreases with increasing ethylene glycol content.Serial Number 102,893, filed September 2a, 1936. Thus from the point ofview of extraction Ethylene glycol and glycerin were excluded as ciencyalone it would appear that the best results m unsuited for t raising oft Solvent power are obtained in the complete absence of ethylene 4c ofaqueous alkali hydroxide solutions for merglycol. However. substantiallysaturated alkali captans, since it had been found t t under t hydroxidesolutions in the absence of ethylene conditions set forth in saidYabrofi application, glycol have the Serious disadvantage of beingethylene glycol and glycerin not only failed t very poor solvents forthe alkali salts of the orraise t solvent power rt alkali hydroxid ganicacids, the high concentrations of alkali 45 solution but actually lowerd it, hydroxide having a salting out effect on the salts, Now we havedis overed that if a aqueous so that the latter form a separate solidphase ethylene glycol solution is substantially saturated w h fr q ycauses rabl ifficulties. with caustic alkali a solution is obtainedwhich Substantially saturated alkali metal hydroxides has goodextraction power for organic weakly are very viscous and difficult tohandle even in the 50 acidic compounds as mercaptans and the like.absence of a solid phase, and under such circum- We use the term causticalkali to designate stances a plugging up of valves, lines, filters,etc., strong alkaline bases, i. e., the alkali metal and is more or lessunavoidable. For this reason it is ammonium hydroxides, alkaline earthhydroxadvantageous to sacrifice a certain amount of ides, quaternaryammonium bases, alkali carextraction efficiency for the sake ofpreventing the precipitation of salts or the weak organic acids.

We have found that, in general, saturated alkali hydroxide solutionscontaining not less than about 25% ethylene glycol are free from thisobjectionable precipitation of salts, and yet possess extractionefliciencies which are not greatly diminished.

The exact amount of ethylene glycol which is required fully to preventthis precipitation varies considerably with the nature of the acidiccompounds absorbed, the type of alkali hydroxide and the concentrationof salts which it is desired to hold in solution, more ethylene glycolusually being required, to dissolve relatively large amounts of thesalts. touse as much as or of ethylene glycol although in general weprefer to use lowest concentrations which successfully preventprecipitation of the salts. In no instance has it been found necessaryto use aqueous ethylene glycol 01 more than about 75% concentration.

When herein speaking of concentration of ethylene glycol we mean torefer to the ratio of ethylene glycol to water, independent of theamount of alkali hydroxide added. Thus a saturated alkali hydroxidesolution containing, for

It may become necessary dium hydroxide or lime water, etc. After removalof acids other than mercaptans, mercaptans are then extracted with asaturated alkali metal hydroxide solution in aqueous ethylene glycol, ashereinbeiore described, under conditions to form two layers, a treatedhydrocarbon type liquid layer and an alkali hydroxide solutioncontaining mercaptides. The mercaptide solution is then steamed to driveoii the mercaptans, or oxidized to convert them to disulfides which canbe separated from the remaining solution by skimming, decanting,centrifuging etc.

Oxidation is most easily carried out with air in the presence of anoxidizing catalyst capable of promoting the oxidation of mercaptides todisulfides, such catalysts being, for instance, the sulfides or oxidesof lead, copper, cobalt, nickel, etc.

We claim as our invention: 1. In the process of separating organicacidreacting substances containedin a water-insoluble neutral or basicorganic liquid, the step comprising treating said liquid with an aqueoussolution of ethylene glycol containing not less than about 25% water,which solution is substantially saturated with an alkali metalhydroxide, the amount of ethylene glycol in said solu tion beingsufllcient to prevent salting out of the alkali metal salts of saidacid-reacting substances from the solution.

2. In the process of separating mercaptans contained in a hydrocarbonliquid, the step comprising treating said liquid with an aqueoussolustion of ethylene glycol containing not less than about 25% water,which solution is saturated, with an alkali metal hydroxide, the amountof ethylene glycol in said solution being sufllcient to prevent saltingout of alkali metal mercaptides from the solutions.

DAVID LOUIS YABROFF. ELLIS R. WHITE.

